Sunday, May 15, 2022

Juno Captures Moon Shadow on Jupiter

The large, dark shadow on the left side of the image was cast by Jupiter’s moon Ganymede.

On Feb. 25, 2022, NASA’s Juno spacecraft completed its mission’s 40th close pass by the giant planet, Jupiter. During this pass, it captured a moon shadow view.

Jupiter’s moon Ganymede cast a large, dark shadow on the left side of the image.

Citizen scientist Thomas Thomopoulos created this enhanced-color image using raw data from the JunoCam instrument (Figure A). At the time the raw image was taken, the Juno spacecraft was about 44,000 miles (71,000 kilometers) above Jupiter’s cloud tops, at a latitude of about 55 degrees south, and 15 times closer than Ganymede, which orbits about 666,000 miles (1.1 million kilometers) away from Jupiter.

An observer at Jupiter’s cloud tops within the oval shadow would experience a total eclipse of the Sun.

Illustration of the approximate geometry of the Ganymede’s shadow projected onto a globe of Jupiter. Credits: Image data: NASA/JPL-Caltech/SwRI/MSSS, Image processing by Brian Swift © CC BY
Figure B: Illustration of the approximate geometry of the Ganymede’s shadow projected onto a globe of Jupiter. Credits: Image data: NASA/JPL-Caltech/SwRI/MSSS, Image processing by Brian Swift © CC BY

Total eclipses are more common on Jupiter than on Earth for several reasons.

Jupiter has four major moons (Galilean satellites) that often pass between Jupiter and the Sun: in seven days, Ganymede transits once; Europa, twice; and Io, four times. And since Jupiter’s moons orbit in a plane close to Jupiter’s orbital plane, the moon shadows are often cast upon the planet.

JunoCam captured this image from very close to Jupiter, making Ganymede’s shadow appear especially large. Figure B, created by citizen scientist Brian Swift using JunoCam data, illustrates the approximate geometry of the visible area projected onto a globe of Jupiter.

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